As conventional display apparatuses, there are known a blackboard using a chalk and a white board using a colored quick-drying ink, etc., in order to draw characters or pictures on the board.
When using chalk, there are problems, however, in sanitation. That is, one problem is the dust occurring when erasing the board in use or after use of the chalk, and the other is the uncomfortable sound occurring when the chalk scrapes the board. Further, there is uncomfortable touch for a tip of a finger when holding the chalk. On the other hand, when using quick-drying ink, there is a problem that the quick-drying ink cannot be easily erased after use, as well as the above problems of the chalk.
Further, another problem is that it is very hard to see the surface of the board due to reflection of the light from the board depending on the angle in observation of the black board or the white board.
Still further, there is a drawing toy which is formed by mixing iron sand into milk white fluid, enclosing the fluid into a small resin capsule, and arranging a plurality of resin capsules so as to constitute the board. In this structure, when drawing characters or pictures on the board, the iron sand is brought up to the surface of the board by using a magnetic bar. When erasing them, the iron sand is removed from the surface of the board by using another magnetic bar.
There is a problem, however, in this drawing toy. That is, it is very hard to partially erase characters or pictures from the board although it is possible to easily draw them on the board. As a result, this is inconvenient in actual use since the whole of the surface of the board is erased at once. Further, there is a problem that it is hard to observe the surface of the board depending on the observation angle since the light is reflected from the surface of the capsules.
Still further, recently, there is a display apparatus which arranges a plurality of photodiodes or liquid crystal elements on a flat board and controls the voltage supplied to them. Various types of this display apparatus have been developed and applied to various products. However, there are problems in this type of display apparatus. That is, although it is possible to realize high quality image in this type of the display apparatus, this display apparatus is very expensive, and the contents to be displayed must be previously input through a predetermined input device. As a result, this type of the display apparatus has no flexibility and convenience in actual use.